JP2012013288A - Water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water heater capable of making a secondary-side outlet temperature accurately coincide with a target temperature.SOLUTION: The electric water heater 1 makes high-temperature water exchange heat with low-temperature water via a heat exchanger 13. A control device 24 makes the low-temperature water partially circulate through a bypass pipe 28 bypassing the heat exchanger 13, when a primary-side necessary flow rate of the high-temperature water required to make the secondary-side outlet temperature coincide with the target temperature determined depending on a set temperature falls within a first region in which the flow rate of the high-temperature water is greatly changed versus a change in a rotational speed of a circulation pump 11. Since the rate of heat transfer from the high-temperature water is reduced due to a reduction in the rate of circulation of the low-temperature water in the heat exchanger 13, the control device 24 makes the flow rate of the high-temperature water fall within a second region except the first region by being increased to compensate for a reduction in the rate of heat transfer. Since the second region is a region in which the secondary-side outlet temperature can be accurately regulated by controlling the rotational speed of the circulation pump 11, the control device 24 enables the secondary-side outlet temperature to accurately coincide with the target temperature.

Description

  The present invention relates to a water heater in which a heat medium circulated by a pump exchanges heat with a heat exchange medium.

  Hot water heater (electric water heater) with a hot water supply function that uses hot water stored in a hot water storage tank as a heat medium, heats low temperature water as a heat exchange medium, and supplies hot water generated by heating the low temperature water to the user ) Is widely known. Such an electric water heater has a hot water heat exchanger that heats the low temperature water by exchanging heat between the low temperature water and the high temperature water, and the high temperature water is configured to circulate through the high temperature pipe of the hot water heat exchanger by a pump. Has been.

  With regard to the electric water heater configured as described above, for example, Patent Document 1 circulates so that the temperature of hot water supplied to the user (secondary outlet temperature of the hot water heat exchanger) becomes a predetermined hot water temperature. An electric water heater is disclosed that controls the primary circulation amount (flow rate of high-temperature water) of a hot water supply heat exchanger by controlling the rotational speed of a pump (hot water supply circulation pump).

Japanese Patent Laid-Open No. 2007-85582

However, since the circulation pump has mechanical parts that generate mechanical resistance such as a bearing and a mechanical part of an electric motor, the influence of the mechanical resistance is large in a low-speed rotation region below a predetermined rotation speed. Pump output changes greatly with changes in rotational speed. Therefore, it becomes difficult to accurately adjust the pump output by controlling the rotational speed of the circulation pump.
Since the primary circulation amount of the hot water heat exchanger changes according to the change in pump output, the primary circulation amount of the hot water heat exchanger can be adjusted accurately in the low-speed rotation region where the pump output cannot be adjusted accurately. Can not. Therefore, in order to accurately adjust the primary circulation amount of the hot water supply heat exchanger, it is preferable to operate the circulation pump in a region of a predetermined rotational speed or higher. Therefore, it is preferable that the primary side circulation amount of the hot water supply heat exchanger is larger than a predetermined flow rate.

  Patent Document 1 does not describe a technique for controlling the primary circulation amount when the primary circulation amount is small, such as when the hot water supply amount is small or when the set value (set temperature) of the hot water supply temperature is low. Therefore, if the hot water supply amount or the set temperature changes when the primary side circulation amount is small, the primary side circulation amount cannot be accurately adjusted, and the secondary side outlet temperature is determined according to the set temperature. There is room for improvement in that the target temperature cannot be accurately matched.

  Then, this invention makes it a subject to provide the water heater which can always make a secondary side exit temperature correspond with target temperature with sufficient precision.

  In order to solve the above problems, the present invention provides a primary side pipe through which a heat medium flows, a secondary side pipe through which a heat exchange medium to exchange heat with the heat medium, the primary side pipe, and the A heat exchanger connected to a secondary side pipe to exchange heat between the heat medium and the heat exchange medium, a pump for circulating the heat medium to the primary side pipe, and bypassing the heat exchanger The flow rate adjustment for adjusting the flow rate ratio between the flow rate of the heat exchange medium flowing through the bypass pipe, the flow rate of the heat exchange medium flowing through the bypass pipe, and the flow rate of the heat exchange medium flowing through the bypass pipe A hot water supply that adjusts the temperature of the heat exchange medium with a flow rate of the heat medium that changes according to a change in the rotation speed of the pump, and matches the temperature of the heat exchange medium with a target temperature. A machine. When the primary side required flow rate, which is the flow rate of the heat medium necessary for making the temperature of the heat exchange medium coincide with the target temperature, is less than a predetermined threshold, the flow rate adjusting mechanism is connected to the bypass pipe. The heat exchange medium is circulated, and the bypass pipe is shut off when the required flow rate on the primary side is equal to or greater than the threshold value.

  According to the present invention, it is possible to provide a water heater that can always make the secondary side outlet temperature coincide with the target temperature with high accuracy.

It is a lineblock diagram of the electric water heater concerning this embodiment. (A), (b) is a graph which shows an example of a pump characteristic. It is a flowchart which shows a hot water supply procedure. It is a flowchart which shows the control procedure when a secondary side flow volume changes, when a mixing valve is closing. It is a flowchart which shows a control procedure when the rotational speed of a circulation pump reaches an upper limit when the mixing valve is open. (A) is a figure which shows the state in which a mixing valve is provided in the branch point of a cryogenic pipe and a bypass pipe, (b) is a figure which shows the state in which an on-off valve and a constant flow valve are provided in a bypass pipe.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, an electric water heater 1 according to an embodiment of the present invention is a water heater in which low temperature water that is a heat exchange medium and high temperature water that is a heat medium exchange heat, and heats low temperature water. The primary side 10 to be heated and the secondary side 20 to supply hot water to the user with hot water generated by heating the low-temperature water.

  The primary side 10 is a pump (circulation pump 11) driven by a motor to send out high temperature water, a hot water storage tank 12 in which high temperature water is stored, and a heat exchanger 13 configured to exchange heat between high temperature water and low temperature water. The circulation pump 11, the hot water storage tank 12, and the heat exchanger 13 are connected by a high temperature pipe 14 (primary side pipe line) through which high temperature water flows. And it is comprised so that measurement of the temperature of the high temperature water taken in into the heat exchanger 13 with the primary side inlet temperature sensor 13a is possible. Hereinafter, the temperature of the high-temperature water measured by the primary side inlet temperature sensor 13a is referred to as a primary side inlet temperature.

  In addition, the high temperature water which distribute | circulates the high temperature pipe 14 of the primary side 10 is heated by the heating apparatus (a heat pump unit, a boiler, etc.) which is not illustrated, for example, and is stored in the hot water storage tank 12.

  On the secondary side 20, a water supply source 21 such as a water supply for supplying low-temperature water and the heat exchanger 13 are connected by a low-temperature pipe 25 (secondary side pipe), and low-temperature water is taken into the heat exchanger 13 to exchange heat. The vessel 13 is configured such that the high-temperature water and the low-temperature water exchange heat and the low-temperature water is heated. Furthermore, the heat exchanger 13 and the faucet 22 are connected by a hot water supply pipe 26 (secondary side pipe line), and hot water generated by heating the low-temperature water in the heat exchanger 13 is used by the user to connect the hot water tap of the faucet 22. It is configured to supply hot water to the user when opened.

  Moreover, the temperature of the low temperature water taken into the heat exchanger 13 from the water supply source 21 is measured by the secondary side inlet temperature sensor 13b, and the temperature of the hot water heated by the heat exchanger 13 is measured by the secondary side outlet temperature sensor 26a. Configured to be. Furthermore, a secondary side flow rate sensor 27 for measuring the flow rate of hot water flowing through the hot water supply pipe 26 is provided. Hereinafter, the temperature of the low temperature water measured by the secondary side inlet temperature sensor 13b is referred to as a secondary side inlet temperature, and the temperature of hot water measured by the secondary side outlet temperature sensor 26a is referred to as a secondary side outlet temperature.

  The electric water heater 1 also has a temperature setting device 23 for setting the temperature of hot water supplied to the user from the faucet 22 (hereinafter referred to as hot water supply temperature), and a set temperature set by the temperature setting device 23. A control device 24 that controls the electric water heater 1 so as to reach a temperature is provided.

And the secondary side 20 of the electric water heater 1 which concerns on this embodiment is equipped with the bypass pipe 28 which bypasses the heat exchanger 13 and connects the low temperature pipe 25 and the hot water supply pipe 26. The bypass pipe 28 branches from the low temperature pipe 25 at a branch point 25 a and is connected to the hot water supply pipe 26 via the mixing valve 29. The mixing valve 29 adjusts the flow rate of the low-temperature water supplied from the water supply source 21 and flowing through the bypass pipe 28 (bypass flow rate) and the flow rate of the low-temperature water flowing through the heat exchanger 13 and the bypass flow rate. This is a flow control mechanism. For example, when the mixing valve 29 is configured so that α% of low-temperature water supplied from the water supply source 21 flows through the bypass pipe 28 when the mixing valve 29 is fully opened, if the opening of the mixing valve 29 is β%, the bypass is performed. In the pipe 28, (α × β / 100)% of low-temperature water supplied from the water supply source 21 flows. Further, when the opening degree of the mixing valve 29 is 0%, that is, when the mixing valve 29 is closed, the bypass pipe 28 is shut off.
The opening degree of the mixing valve 29 is controlled by the control device 24.

The secondary outlet temperature of the electric water heater 1 configured as described above is adjusted by the circulation amount of the high-temperature water on the primary side 10, and the control device 24 allows the secondary outlet temperature when the user opens the hot water tap of the faucet 22. The set temperature becomes the hot water supply temperature based on the side inlet temperature, the secondary side outlet temperature, the flow rate of hot water measured by the secondary side flow rate sensor 27 (hereinafter referred to as the secondary side flow rate), the primary side inlet temperature, etc. The electric water heater 1 is controlled.
Hereinafter, the circulation amount of high-temperature water on the primary side 10 is referred to as a primary-side circulation amount.
For example, the control device 24 controls the rotational speed of the circulation pump 11 by feedback control in which a deviation between the secondary side outlet temperature and the set temperature is fed back so that the deviation between the secondary side outlet temperature and the set temperature becomes zero. Adjust the primary circulation rate. At this time, the control device 24 adjusts the rotational speed of the circulation pump 11 to adjust the primary circulation amount.

The characteristic (pump characteristic) of the circulation pump 11 is a characteristic curve showing the relationship between the rotational speed and the pump output (corresponding to the primary circulation amount in this embodiment) as shown in FIG. As shown, the pump output increases as the rotational speed increases, and the circulation rate of high-temperature water increases.
Since the secondary side outlet temperature is determined by the primary side inlet temperature and the circulation amount of the high-temperature water, the control device 24 shown in FIG. 1 has the secondary side outlet temperature when the secondary side outlet temperature is lower than the set temperature. Set the circulation rate of hot water based on the secondary side outlet temperature and the primary side inlet temperature so that the deviation between the secondary side outlet temperature and the set temperature becomes zero, The rotational speed of the circulation pump 11 is determined so that the primary circulation amount becomes the set circulation amount.

  Specifically, the control device 24 increases the primary circulation amount by operating the circulation pump 11 at a higher rotational speed as the deviation between the set temperature and the secondary side inlet temperature increases. The smaller the deviation, the lower the primary circulation amount by operating the circulation pump 11 at a lower rotational speed. Further, as the flow rate of the hot water (secondary flow rate) measured by the secondary flow rate sensor 27 increases, the circulation pump 11 is operated at a higher rotational speed to increase the primary circulation rate, and as the secondary flow rate decreases, The circulation pump 11 is operated at a low rotational speed to reduce the primary circulation amount. Further, the control device 24 operates the circulation pump 11 at a higher rotational speed as the primary side inlet temperature is lower to increase the primary side circulation amount, and operates the circulation pump 11 at a lower rotational speed as the primary side inlet temperature is higher. Reduce primary circulation.

Thus, the control device 24 determines the primary circulation amount based on the set temperature, the primary inlet temperature, the secondary inlet temperature, and the secondary flow rate, and further obtains the determined primary circulation amount. The rotational speed of the circulation pump 11 is determined.
The primary circulation amount determined by the control device 24 based on the set temperature, the primary inlet temperature, the secondary inlet temperature, and the secondary flow rate is referred to as a primary required flow rate.

However, the pump output (primary circulation amount) of the circulation pump 11 is, for example, as shown in FIG. 2 (a), a region in which the pump output (primary circulation amount) changes greatly according to the change in the rotational speed (the first circulation amount). 1 region) and other regions (second region) in many cases. In this case, since the primary region has a large change in the primary circulation amount with respect to the change in the rotation speed of the circulation pump 11, it is difficult to accurately adjust the primary circulation amount by controlling the rotation speed of the circulation pump 11.
On the other hand, in the second region, the change in the primary circulation amount with respect to the change in the rotation speed of the circulation pump 11 is smaller than that in the first region, and the primary circulation amount can be accurately adjusted by controlling the rotation speed of the circulation pump 11. . Therefore, in order to control the rotational speed of the circulation pump 11 and accurately adjust the primary circulation amount, it is preferable that the required primary flow rate is in the second region.

  Therefore, the control device 24 in the present embodiment is configured such that the determined primary required flow rate falls within the second region shown in FIG. With this configuration, the control device 24 can control the rotational speed of the circulation pump 11 to accurately adjust the primary circulation amount.

  The point that becomes the boundary between the first region and the second region is referred to as an “inflection point P”, and the primary circulation amount at the inflection point P is referred to as a boundary circulation amount L1. The boundary circulation amount L1 is a characteristic value determined by the configuration of the circulation pump 11 (see FIG. 1) and the like. When the pump characteristic of the circulation pump 11 is such that the increase rate of the primary circulation amount decreases as the rotation speed increases as shown in FIG. 2A, for example, the primary side circulation with respect to the increase rate of the rotation speed. A configuration in which the primary circulation amount at which the rate of increase in the amount reaches a predetermined value (for example, “1”) is considered as the inflection point P. The boundary circulation amount L1 at the inflection point P is the performance of the circulation pump 11. What is necessary is just to set suitably based on the specification etc. which are requested | required of the electric water heater 1. FIG.

  For example, when the rated maximum rotation speed of the circulation pump 11 is 6000 rpm, the inflection point P can be considered to be around 2000 rpm (2000 to 1500 rpm). That is, a configuration in which the inflection point P is a rotational speed of about 1/3 to 1/4 of the maximum rotational speed (6000 rpm) is conceivable.

  Further, for example, as shown in FIG. 2B, in the case of the circulation pump 11 having a pump characteristic having a region where the primary circulation amount changes substantially linearly with the change of the rotation speed, the primary circulation is performed. The region where the amount changes linearly may be the first region, the other region may be the second region, and the boundary point may be the “inflection point P”.

  As described above, in the present embodiment, a region where the primary circulation amount changes greatly with respect to a change in the rotational speed of the circulation pump 11 is defined as a first region, and the other region is defined as a second region. Then, the inflection point P (boundary circulation amount L1) serving as a boundary between the first region and the second region is appropriately set as a characteristic value of the circulation pump 11.

  In the control device 24 according to the present embodiment, the primary side required flow rate determined based on the set temperature, the primary side inlet temperature, the secondary side inlet temperature, and the secondary side circulation amount is equal to or less than the boundary circulation amount L1, and the first region When in, the mixing valve 29 is opened to allow the low-temperature water to flow through the bypass pipe 28. The flow rate of the low-temperature water flowing through the heat exchanger 13 decreases, and the amount of heat (heat transfer amount) transferred from the high-temperature water to the low-temperature water decreases. Then, the control device 24 increases the rotation speed of the circulation pump 11 to compensate for the reduced heat transfer amount and increases the primary circulation amount, and enters the second region when the primary circulation amount exceeds the boundary circulation amount L1. . By making the primary-side circulation amount thus increased as a new primary-side required flow rate, the primary-side required flow rate can be put into the second region.

In addition, the control apparatus 24 does not open the mixing valve 29, interrupts the bypass pipe 28, and does not distribute low temperature water to the bypass pipe 28, when the primary side required flow volume is more than the boundary circulation amount L1.
That is, the control device 24 sets the boundary circulation amount L1 as a predetermined threshold value, and opens the mixing valve 29 when the primary-side required flow rate is smaller than the boundary circulation amount L1, and when the primary-side required flow rate is equal to or greater than the boundary circulation amount L1. The mixing valve 29 is closed.

When the user changes the opening of the hot water tap of the faucet 22 and the secondary flow rate changes, or when the user operates the temperature setting device 23 and changes the set temperature, the control device 24 responds to the set temperature. The target temperature is determined and the primary circulation amount is adjusted within the range of the second region, so that the secondary outlet temperature can be matched with the determined target temperature. The second region is a region in which the change in the primary circulation amount with respect to the change in the rotation speed of the circulation pump 11 is small, and the primary circulation amount can be accurately adjusted by controlling the rotation speed of the circulation pump 11. Therefore, even when the user changes the opening of the hot water tap of the faucet 22 or when the set temperature is changed, the secondary outlet temperature is set to a target temperature determined according to the changed set temperature. It can be made to coincide with accuracy, and hot water having a set temperature as the hot water supply temperature can be stably supplied to the user.
The target temperature determined by the control device 24 may be equal to the set temperature set by the user, or is set to a temperature higher than the set temperature in consideration of a temperature drop when hot water flows to the faucet 22. Also good.

With reference to FIG. 3, the procedure in which the control device 24 controls the electric water heater 1 to supply hot water to the user will be described (hereinafter, refer to FIGS. 1 and 2 as appropriate). The procedure for supplying hot water to the user is hereinafter referred to as a hot water supply procedure.
When the user opens the hot water tap when the faucet 22 is closed, low-temperature water flows in the order of the low-temperature pipe 25, the heat exchanger 13, and the hot water pipe 26 due to the water pressure of the water supply source 21. 22 is discharged. Therefore, the control device 24 detects that the hot water tap of the faucet 22 has been opened by detecting an increase in the secondary flow rate measured by the secondary flow rate sensor 27, and the target temperature is supplied from the water supply source 21. When the temperature is lower than the temperature of the low-temperature water (secondary inlet temperature), the circulation pump 11 is operated to heat the low-temperature water with the heat exchanger 13.

  That is, while the secondary flow rate does not increase from “0”, the control device 24 determines that the hot water tap of the faucet 22 is closed (step S1 → No), and closes the mixing valve 29 (step S2). The bypass pipe 28 is shut off. On the other hand, when the secondary side flow rate increases from “0”, the control device 24 determines that the hot water tap of the faucet 22 has been opened (step S1 → Yes), and the primary side inlet temperature, the secondary side inlet temperature, the secondary side Based on the flow rate and the target temperature, the circulation amount of the high-temperature water (primary side required flow rate) necessary to make the secondary side outlet temperature coincide with the target temperature is determined (step S3).

The required flow rate on the primary side can be determined by the following equation (1), for example.

Primary side required flow rate = (Target temperature-Secondary side inlet temperature) x Secondary side flow rate
/ (Primary side inlet temperature-Primary side outlet predicted temperature) (1)

For example, when the secondary side inlet temperature is 10 ° C., the target temperature is 40 ° C., the primary side inlet temperature is 80 ° C., the primary side outlet predicted temperature is 12 ° C., and the secondary side flow rate is 5 L / min, the primary side required flow rate Is
(40-10) × 5 / (80-12) = 2.2 [L / min]
Can be determined.
The primary side outlet predicted temperature is a predicted value of the temperature of the high-temperature water (primary side outlet temperature) after heat exchange in the heat exchanger 13. The primary side outlet temperature is predicted to be a predetermined temperature higher than the secondary side inlet temperature, and this predetermined temperature is a characteristic value determined by the configuration of the heat exchanger 13 or the like. In the present embodiment, the predetermined temperature is 2 ° C., and the primary side outlet predicted temperature is 12 ° C., which is 2 ° C. higher than the secondary side inlet temperature (10 ° C.).
In addition, the temperature sensor (not shown) which measures the primary side exit temperature of the heat exchanger 13 may be provided, and the primary side required flow rate may be calculated using the primary side exit temperature measured by the temperature sensor.

  The control device 24 compares the determined primary required flow rate with the boundary circulation amount L1 that becomes the inflection point P (step S4). If the determined primary required flow rate is equal to or greater than the boundary circulation amount L1 (step S4 → Yes), the controller 24 determines the rotational speed of the circulation pump 11 based on the determined primary required flow rate (step S5). ), The circulating pump 11 is operated at the determined rotational speed (step S6).

For example, when the boundary circulation amount L1 of the circulation pump 11 is 2 L / min and the determined primary side required flow rate is 2.2 L / min, the control device 24 obtains the primary side required flow rate of 2.2 L / min. The rotation speed of the circulation pump 11 is determined with reference to the pump characteristics shown in FIGS. 2A and 2B (step S5), and the circulation pump 11 is operated at the determined rotation speed (step S6).
While the hot-water tap is open (step S7 → No), the control device 24 constantly monitors the primary side inlet temperature, the secondary side inlet temperature, the secondary side flow rate, and the set temperature, and the user supplies hot water to the faucet 22. When the secondary side flow rate is changed by changing the opening of the stopper, or when the user operates the temperature setting device 23 and the set temperature is changed, the secondary side outlet temperature is changed to the changed set temperature. The circulating pump 11 is operated by determining again the primary required flow rate and the rotational speed of the circulating pump 11 so as to coincide with the target temperature determined accordingly. That is, the rotational speed of the circulation pump 11 is controlled (step S8).

  When the hot water tap is closed (step S7 → Yes), the control device 24 closes the mixing valve 29 (step S2) and ends the hot water supply procedure. The control device 24 determines that the hot water tap is closed when the secondary flow rate becomes “0”.

On the other hand, when the determined primary required flow rate is smaller than the boundary circulation amount L1 (step S4 → No), the control device 24 sets the opening degree of the mixing valve 29 (step S9).
For example, when the secondary side inlet temperature is 20 ° C, the target temperature is 40 ° C, the primary side inlet temperature is 80 ° C, the primary side outlet predicted temperature is 22 ° C, and the secondary side flow rate is 5 L / min, the primary side required flow rate Is determined by equation (1) as follows.
(40-20) × 5 / (80-22) = 1.7 [L / min]
In this case, the required flow rate on the primary side (1.7 L / min) is smaller than the boundary circulation amount L1 (2 L / min) and enters the first region shown in FIGS. At this time, the control device 24 sets the opening degree of the mixing valve 9 based on the target temperature, the primary side inlet temperature, and the secondary side inlet temperature immediately after the faucet 22 is opened.

  For example, if the map showing the relationship between the temperature difference between the target temperature and the primary inlet temperature and the opening of the mixing valve 29 is set in advance and stored in a storage unit (not shown) of the control device 24, the control is performed. The device 24 refers to the map based on the temperature difference between the target temperature determined according to the set temperature set by the temperature setting device 23 and the primary inlet temperature measured by the primary inlet temperature sensor 13a, and the mixing valve 29 Can be set.

  For example, when the temperature difference between the target temperature and the primary inlet temperature is 40 ° C., the opening degree of the mixing valve 29 is set to 50%, and when the temperature difference between the target temperature and the primary inlet temperature is 15 ° C., the mixing valve 29 is set. If the temperature difference between the target temperature and the primary inlet temperature is 40 ° C., the controller 24 sets the opening of the mixing valve 29 to 50%. If the temperature difference between the target temperature and the primary inlet temperature is 15 ° C., the control device 24 sets the opening of the mixing valve 29 to 10%.

  Further, the opening degree of the mixing valve 29 may be corrected according to the secondary side inlet temperature. That is, when the secondary side inlet temperature is high, the amount of the low temperature water flowing through the bypass pipe 28 is increased to reduce the low temperature water taken into the heat exchanger 13, and the heat exchanger 13 transfers heat from the high temperature water to the low temperature water. Reduces the amount of heat transferred. For example, when the secondary inlet temperature is 20 ° C., if the opening of the mixing valve 29 is corrected so as to open 5%, the temperature difference between the target temperature and the primary inlet temperature when the secondary inlet temperature is 20 ° C. Is 40 ° C., the control device 24 sets the opening of the mixing valve 29 to 55% (50% + 5%).

  The opening degree of the mixing valve 29 may be set so that, for example, the required flow rate on the primary side exceeds the boundary circulation amount L1 by about 20 to 30%. If the primary side required flow rate is configured to greatly exceed the boundary circulation amount L1, the energy consumption for maintaining the rotational speed of the circulation pump 11 increases, and the efficiency decreases. In addition, if the primary side required flow rate is less than the boundary circulation amount L1, the primary side circulation rate enters the first region when the primary side required flow rate becomes small, and the primary side circulation rate can be adjusted with high accuracy. It becomes difficult. In view of the above, the opening degree of the mixing valve 29 may be set so that the primary-side required flow rate suitably exceeds the boundary circulation amount L1. The above 20 to 30% is an example, and a value based on the performance of the circulation pump 11, specifications required for the electric water heater 1, and the like can be appropriately set.

  When the opening degree of the mixing valve 29 is set (step S9), the control device 24 opens the mixing valve 29 so as to reach the set opening degree (step S10), and the secondary side outlet temperature is equal to the target temperature. The rotation speed of the circulation pump 11 is controlled so as to match, that is, the deviation between the secondary side outlet temperature and the target temperature becomes zero (step S11), and the circulation pump 11 is operated. With this configuration, the control device 24 can control the rotation speed of the circulation pump 11 in a state where the primary circulation amount enters the second region.

  Then, the control device 24 executes step S11 until the hot water tap is closed to control the rotational speed of the circulation pump 11 (step S12 → No), and when the hot water tap is closed (step S12 → Yes), the mixing valve 29 is closed. The bypass pipe 28 is shut off (step S2), and the hot water supply procedure is terminated.

As described above, the electric water heater 1 (see FIG. 1) according to the present embodiment has the mixing valve 29 (see FIG. 1) when the required flow rate on the primary side is smaller than the boundary circulation amount L1 and enters the first region in the hot water supply procedure. ) Is opened and low temperature water is mixed with hot water flowing through the hot water supply pipe 26 (see FIG. 1) via the bypass pipe 28 (see FIG. 1). Therefore, the amount of low-temperature water taken into the heat exchanger 13 (see FIG. 1) decreases, and the amount of heat transferred from the high-temperature water to the low-temperature water in the heat exchanger 13 decreases.
Therefore, the control device 24 (see FIG. 1) increases the rotational speed of the circulation pump 11 (see FIG. 1) in order to compensate for the decrease in the amount of heat transferred from the high temperature water to the low temperature water in the heat exchanger 13. Increase primary circulation.
That is, in the electric water heater 1, when the required flow rate on the primary side is in the first region, the circulation amount on the primary side is higher than when the mixing valve 29 is closed and the low-temperature water is not mixed with the hot water flowing through the hot water supply pipe 26. The primary circulation amount enters the second region shown in FIGS. 2A and 2B.
On the other hand, when the primary-side required flow rate is larger than the boundary circulation amount L1 and enters the second region, the mixing valve 29 of the electric water heater 1 is closed and the bypass pipe 28 (see FIG. 1) is shut off.

  When the secondary flow rate changes or the set temperature is changed, the control device 24 (see FIG. 1) adjusts the rotational speed of the circulation pump 11 (see FIG. 1) to adjust the primary circulation amount. The secondary side outlet temperature can be adjusted with high accuracy, and the target temperature determined in accordance with the changed set temperature can be matched with high accuracy. With this configuration, hot water having the set temperature as the hot water supply temperature can be stably supplied to the user from the tap 22.

Since the primary circulation amount is a value determined according to the rotational speed of the circulation pump 11 (see FIG. 1), the control device 24 (see FIG. 1) determines the primary required flow rate in step S3. In addition, the rotation speed of the circulation pump 11 corresponding to the determined primary-side required flow rate is determined, and the opening and closing of the mixing valve 29 (see FIG. 1) are set according to the determined rotation speed of the circulation pump 11. Also good. Specifically, the control device 24 opens the mixing valve 29 when the determined rotation speed of the circulation pump 11 is lower than the predetermined rotation speed, and the determined rotation speed of the circulation pump 11 is determined in advance. The mixing valve 29 may be closed when the rotation speed is equal to or higher than the predetermined rotation speed.
In this case, the mixing valve 29 is opened when the primary side required flow rate is smaller than the boundary circulation amount L1 by setting the rotation speed of the circulation pump 11 at which the primary side circulation amount becomes the boundary circulation amount L1 to a predetermined rotation speed. The same effect can be obtained.

  Next, when the circulating pump 11 (see FIG. 1) is operated with the mixing valve 29 (see FIG. 1) closed, the user changes the opening of the hot water tap of the faucet 22 to the secondary side. A control procedure when the flow rate is changed will be described (see FIGS. 1 and 2 as appropriate). This control procedure is executed by the control device 24 in step S8 shown in FIG.

  As shown in FIG. 4, if the secondary flow rate does not change while the control device 24 is operating the circulation pump 11 when the mixing valve 29 is closed (step S20 → No), the control device 24 Although the rotational speed of the circulation pump 11 is controlled without opening the mixing valve 29 (step S26), when the secondary side flow rate changes (step S20 → Yes), the control device 24 determines that the primary side inlet temperature, two The primary side required flow rate is determined based on the secondary side inlet temperature, the secondary side flow rate, and the target temperature (step S21). And the control apparatus 24 opens the mixing valve 29, when the determined primary side required flow rate does not reduce from the primary side required flow rate determined before (for example, step S3 of FIG. 3) (step S22-> No). Instead, the rotational speed of the circulation pump 11 is controlled (step S26).

On the other hand, when the primary side required flow rate is smaller than the previously determined primary side required flow rate (step S22 → Yes), the control device 24 compares the primary side required flow rate with the boundary circulation amount L1 (step S23), and the primary side required flow rate. When the flow rate is equal to or greater than the boundary circulation amount L1 (step S23 → Yes), the rotational speed of the circulation pump 11 is controlled without opening the mixing valve 29 (step S26).
When the primary side required flow rate is smaller than the boundary circulation amount L1 (step S23 → No), the control device 24 sets the opening of the mixing valve 29 in the same procedure as step S9 in FIG. 3 (step S24), and the mixing is performed. The valve 29 is gradually opened to the set opening (step S25). And the control apparatus 24 controls the rotational speed of the circulation pump 11 in the state which the mixing valve 29 opened (step S26).

  The control device 24 measures the secondary side outlet temperature with the secondary side outlet temperature sensor 26a, calculates the deviation between the target temperature and the secondary side outlet temperature, and rotates the circulation pump 11 so that the deviation converges to zero. When a series of cycles for changing the speed is a “circulation pump control cycle”, the control device 24 is preferably configured to open the mixing valve 29 in a time several to several tens of times the control cycle of the circulation pump. is there.

  When the mixing valve 29 is opened rapidly, the flow rate of the low-temperature water flowing through the heat exchanger 13 decreases rapidly, and the amount of heat transferred from the high-temperature water to the low-temperature water decreases rapidly. Furthermore, low temperature water flows into the hot water supply pipe 26 at a stretch. Therefore, the secondary side outlet temperature rapidly decreases, and the control device 24 performs control so that the rotational speed of the circulation pump 11 is rapidly increased. As a result, a phenomenon such as overshoot or hunting occurs in the rotational speed of the circulation pump 11 and the control is not preferable. Moreover, the hot water supply temperature supplied to the user becomes unstable.

  Therefore, the control device 24 opens the mixing valve 29 in a time sufficiently longer than the control period of the circulation pump, and stably controls the rotation speed of the circulation pump 11. For example, when the control period of the circulation pump is 1 second and the set opening degree of the mixing valve 29 is 50%, the control device 24 is configured to open the mixing valve 29 in 10 seconds. The 10 seconds described above is an example, and the time for opening the mixing valve 29 is a design value that can be set as appropriate according to the configuration of the electric water heater 1.

  When the secondary pump flow rate changes when the circulating pump 11 is operated with the mixing valve 29 closed, the control device 24 executes the control procedure shown in FIG. And the primary circulation amount can be put in the second region shown in FIGS. 2 (a) and 2 (b). Thereafter, the primary circulation amount can be accurately adjusted by controlling the rotational speed of the circulation pump 11. Therefore, even when the user changes the opening of the hot water tap of the faucet 22 or when the set temperature is changed, the secondary side outlet temperature matches the target temperature determined in accordance with the set temperature with high accuracy. Hot water having a set temperature as the hot water supply temperature can be stably supplied to the user.

  Further, when the control device 24 opens the mixing valve 29, it opens in a time sufficiently longer than the control cycle of the circulation pump 11. With this configuration, the control device 24 can stably control the rotation speed of the circulation pump 11.

  Even when the set temperature is changed when the control device 24 is operating the circulation pump 11 with the mixing valve 29 closed, by executing step S21 and subsequent steps of the control procedure shown in FIG. The mixing valve 29 can be opened as necessary.

  Next, the control procedure when the rotational speed of the circulation pump 11 reaches the upper limit and the primary circulation amount reaches the upper limit when the mixing valve 29 is opened will be described (hereinafter, FIG. 1 and FIG. reference). This control procedure is executed by the control device 24 when the rotational speed of the circulation pump 11 reaches the upper limit in step S11 shown in FIG.

As shown in FIG. 5, if the secondary flow rate does not change when the mixing valve 29 is opened (step S30 → No), the control device 24 sets the circulation pump 11 without closing the mixing valve 29. Although the rotational speed is controlled (step S35), when the secondary flow rate has changed (step S30 → Yes), the control device 24 compares the target temperature with the secondary outlet temperature (step S31).
When the secondary side outlet temperature is equal to or higher than the target temperature (step S31 → No), the control device 24 controls the rotational speed of the circulation pump 11 without closing the mixing valve 29 (step S35).

  On the other hand, when the secondary side outlet temperature is lower than the target temperature (step S31 → Yes), the control is performed when the rotational speed of the circulation pump 11 does not reach the upper limit and is not the output upper limit of the circulation pump 11 (step S32 → No). The device 24 controls the rotation speed of the circulation pump 11 without closing the mixing valve 29 (step S35), but when the rotation measure of the circulation pump 11 reaches the upper limit and the output upper limit of the circulation pump 11 is reached (step S32 → Yes), the control device 24 gradually closes the mixing valve 29 (step S33). At this time, the control device 24 closes the mixing valve 29 over several times to several tens of times the control period of the circulation pump, as in the case of gradually opening the mixing valve 29 in step S25 of FIG. Valve to avoid a rapid rise in secondary outlet temperature.

  Then, after closing the mixing valve 29 (step S33), the control device 24 controls the rotational speed of the circulation pump 11 (step S35) while the mixing valve 29 is fixed to the closed valve (step S34).

When the secondary side outlet temperature is lower than the target temperature, the control device 24 increases the rotation speed of the circulation pump 11 to increase the pump output, and controls the rotation speed of the circulation pump 11 so as to increase the primary circulation amount. To do. However, when the rotation measure of the circulation pump 11 is the upper limit, the control device 24 cannot further increase the rotation speed of the circulation pump 11 and cannot increase the secondary side outlet temperature.
In such a case, the control device 24 according to the present embodiment closes the mixing valve 29 and stops mixing hot water and low temperature water in the hot water supply pipe 26. A decrease in the temperature of the hot water flowing through the hot water supply pipe 26 due to the temperature of the low temperature water is suppressed, and the secondary side outlet temperature rises. Then, the secondary outlet temperature can be increased to the target temperature without increasing the rotational speed of the circulation pump 11.

  At this time, the control device 24 avoids a rapid rise in the secondary outlet temperature by gradually closing the mixing valve 29, and a phenomenon such as overshoot or hunting occurs in the rotational speed of the circulation pump 11. To prevent you from doing.

  Thus, when the rotational speed of the circulation pump 11 reaches the upper limit with the mixing valve 29 opened, the secondary side outlet temperature is controlled by closing the mixing valve 29 and controlling the rotational speed of the circulation pump 11. Can be accurately matched with the target temperature, and hot water having the set temperature as the hot water supply temperature can be stably supplied to the user.

As described above, the electric water heater 1 (see FIG. 1) according to the present embodiment bypasses the low-temperature water supplied from the water supply source 21 (see FIG. 1) by the heat exchanger 13 (see FIG. 1). A bypass pipe 28 (see FIG. 1) to be circulated and a mixing valve 29 (see FIG. 1) are provided, and the control device 24 (see FIG. 1) is required on the primary side to make the secondary side outlet temperature coincide with the target temperature. The electric water heater 1 is controlled so that the flow rate falls in the second region shown in FIGS. 2A and 2B. With this configuration, the control device 24 can accurately adjust the primary circulation amount by controlling the rotational speed of the circulation pump 11 (see FIG. 1), and thus can accurately adjust the secondary outlet temperature.
Therefore, when the opening degree of the hot water tap of the faucet 22 is changed or the set temperature is changed, the control device 24 can accurately match the secondary side outlet temperature with the target temperature, and the set temperature is set to the hot water temperature. It has an excellent effect of stably supplying hot water to the user.

Note that the design of this embodiment can be changed as appropriate without departing from the spirit of the invention.
For example, as shown in FIG. 1, the present invention is not limited to the configuration in which the mixing valve 29 is provided at the junction of the bypass pipe 28 and the hot water supply pipe 26, and as shown in FIG. A configuration in which a mixing valve 29 is provided at the branch point may be employed. Even if it is this structure, there exists an effect similar to the electric water heater 1 shown in FIG.

  Further, as shown in FIG. 6B, the mixing valve 29 (see FIG. 1) is not provided, and the on-off valve 28a for opening and closing the bypass pipe 28 and the bypass flow rate of the low-temperature water flowing through the bypass pipe 28 are kept constant. It is also possible to adopt a configuration provided with a constant flow valve 28b (orifice or the like) serving as a valve mechanism for this purpose. In this configuration, when the on-off valve 28a is opened, low-temperature water flows through the bypass pipe 28 at a flow rate set by the constant flow valve 28b, and the flow rate of low-temperature water flowing through the heat exchanger 13 (see FIG. 1) The flow rate ratio of the bypass flow rate of the low-temperature water flowing through the bypass pipe 28 is determined. When the on-off valve 28a is closed, the bypass pipe 28 is shut off, and all the low-temperature water supplied from the water supply source 21 (see FIG. 1) flows through the heat exchanger 13. As described above, the on-off valve 28a and the constant flow valve 28b adjust the flow rate ratio between the flow rate of the low-temperature water flowing through the heat exchanger 13 (see FIG. 1) and the flow rate of the low-temperature water flowing through the bypass pipe 28. Become an adjustment mechanism.

As shown in FIG. 6B, in the case of the configuration including the on-off valve 28a, the control device 24 (see FIG. 1) sets the on-off valve 28a instead of the mixing valve 29 (see FIG. 1) in step S2 of FIG. By closing the valve and shutting off the bypass pipe 28 and opening the on-off valve 28a in step S10, the electric water heater 1 can be controlled in the same manner as when the mixing valve 29 is provided.
When the secondary flow rate changes with the on-off valve 28a closed, the control device 24 opens the on-off valve 28a instead of the mixing valve 29 in step S25 of FIG. Although the on-off valve 28a opens rapidly, the provision of the constant flow valve 28b suppresses the rapid increase in the flow rate of the low-temperature water flowing through the bypass pipe 28 (see FIG. 1), and the heat exchanger 13 (see FIG. 1). ), The flow rate of the low-temperature water flowing through is reduced at once. Therefore, a rapid decrease in the secondary side outlet temperature is avoided. Thus, the control device 24 can control the electric water heater 1 by opening the on-off valve 28a in the same manner as when the mixing valve 29 is provided.

  When the rotational speed of the circulation pump 11 reaches the upper limit with the on-off valve 28a opened, the control device 24 (see FIG. 1) replaces the mixing valve 29 (see FIG. 1) in step S33 of FIG. Then, the on-off valve 28a is closed to shut off the bypass pipe 28. The on-off valve 28a closes rapidly, but by providing the constant flow valve 28b, for a while after the on-off valve 28a is closed, low temperature water in the bypass pipe 28 is mixed with hot water flowing through the hot water supply pipe 26. A rapid rise in the secondary outlet temperature is avoided. Therefore, the control device 24 can control the electric water heater 1 by closing the on-off valve 28a as in the case where the mixing valve 29 is provided.

  As shown in FIG. 6B, the mixing valve 29 (see FIG. 1) is not provided. As shown in FIG. 6B, the open / close valve 28a for opening and closing the bypass pipe 28 and the constant flow valve 28b may be used. There exists an effect equivalent to the electric water heater 1 shown.

In this embodiment, as shown in FIG. 1, the high-temperature water stored in the hot water storage tank 12 is circulated by the circulation pump 11, but the present invention is applied to an electric water heater that circulates a refrigerant such as CO ₂ by the circulation pump 11. The invention can also be applied.
Further, the present invention can also be applied to an electric water heater that does not include the hot water storage tank 12 and circulates high-temperature water or refrigerant heated by a refrigeration apparatus (not shown) directly by the circulation pump 11.
Further, the present invention is not limited to an electric water heater (hot water heater) that heats low-temperature water (heat exchange medium) with high-temperature water (heat medium), but also to a water heater that cools the heat exchange medium with a refrigerant (heat medium). The invention can be applied.

  As described above, according to the present invention, the flow rate of the heat medium (primary circulation amount) necessary to match the temperature of the low-temperature water that is the heat exchange medium with the target temperature determined according to the set temperature. When the required flow rate on the primary side is in a region (first region) that is smaller than a predetermined threshold (boundary circulation amount L1), the heat exchanger 13 can be bypassed and a part of the heat exchange medium can be circulated. Accordingly, the flow rate of the low-temperature water in the heat exchanger 13 is reduced, the amount of heat transferred from the heat medium to the low-temperature water is reduced in the heat exchanger 13, and the primary side required flow rate is increased to compensate for the decrease in the heat transfer amount. it can. And the primary side required flow volume can be put into 2nd area | regions other than a 1st area | region. The second region is a region in which the flow rate of the heat medium changes small according to the change in the rotation speed of the circulation pump 11, and the flow rate of the heat medium can be accurately adjusted by controlling the rotation speed of the circulation pump 11. Therefore, the temperature of the low temperature water which is the secondary side outlet temperature can be adjusted with high accuracy by controlling the rotational speed of the circulation pump 11, and the secondary side outlet temperature can be made to coincide with the target temperature with high accuracy.

1 Electric water heater (water heater)
10 Primary side 11 Circulation pump (pump)
13 Heat exchanger 14 High-temperature pipe (primary side pipe line)
20 Secondary side 24 Control device 25 Cryogenic pipe (secondary side pipe line)
26 Hot water supply pipe (secondary pipe line)
28 Bypass pipe 28a On-off valve (flow rate adjusting mechanism)
28b Constant flow valve (Flow control mechanism)
29 Mixing valve (Flow control mechanism)
L1 Boundary circulation amount (threshold)

Claims (5)

A primary conduit through which a heat medium flows;
A secondary side pipe through which a heat exchange medium to exchange heat with the heat medium flows;
A heat exchanger connected to the primary side pipe and the secondary side pipe to exchange heat between the heat medium and the heat exchange medium;
A pump for circulating the heat medium through the primary side pipe line;
A bypass pipe provided in the secondary side pipe line so as to bypass the heat exchanger;
A flow rate adjusting mechanism for adjusting a flow rate ratio between the flow rate of the heat exchange medium flowing through the heat exchanger and the flow rate of the heat exchange medium flowing through the bypass pipe;
A water heater that adjusts the temperature of the heat exchange medium with the flow rate of the heat medium that changes in accordance with a change in the rotation speed of the pump, and matches the temperature of the heat exchange medium with a target temperature,
The flow rate adjusting mechanism includes:
When the primary side required flow rate, which is the flow rate of the heat medium necessary to match the temperature of the heat exchange medium with the target temperature, is less than a predetermined threshold, the heat exchange medium is circulated through the bypass pipe,
When the primary-side required flow rate is equal to or higher than the threshold value, the bypass pipe is shut off.   The water heater according to claim 1, wherein the flow rate adjusting mechanism includes a mixing valve.   2. The flow rate adjusting mechanism includes an on-off valve that opens and closes the bypass pipe, and a valve mechanism that maintains a constant flow rate of the heat exchange medium flowing through the bypass pipe. The water heater described in 1.   When the primary side required flow rate is less than the threshold, the flow rate of the heat exchange medium flowing through the bypass pipe is set based on the target temperature and the temperature of the heat medium flowing through the primary side pipe line. The water heater according to any one of claims 1 to 3, wherein A primary conduit through which a heat medium flows;
A secondary side pipe through which a heat exchange medium to exchange heat with the heat medium flows;
A heat exchanger connected to the primary side pipe and the secondary side pipe to exchange heat between the heat medium and the heat exchange medium;
A pump for circulating the heat medium through the primary side pipe line;
A bypass pipe provided in the secondary side pipe line so as to bypass the heat exchanger;
A flow rate adjusting mechanism for adjusting a flow rate ratio between the flow rate of the heat exchange medium flowing through the heat exchanger and the flow rate of the heat exchange medium flowing through the bypass pipe;
A water heater that adjusts the temperature of the heat exchange medium with the flow rate of the heat medium that changes in accordance with a change in the rotation speed of the pump, and matches the temperature of the heat exchange medium with a target temperature,
The flow rate adjusting mechanism includes:
When the rotational speed of the pump is lower than a predetermined rotational speed, the heat exchange medium is circulated through the bypass pipe,
The hot water heater characterized by shutting off the bypass pipe when the rotational speed of the pump is equal to or higher than the predetermined rotational speed.

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